Discomfort in my right Testicle, occasionally my left

I'm 15 years old, going on 16. I have noticed an increasing pain in my right testicle, occasionally in the left as well. The chord that holds the right testicle seems to have swollen up a bit with a pea sized lump behind the testicle. I'm just slightly concerned, and was wondering if any doctor or anyone that has experienced something like this could tell me anything that it may be?
I have read numerous items of information on here and many other sites, and it seems to be similar to something called 'Epididymitis'... Could this be it?

Extra information:
I get slight pains in my lower back and the top of my leg due to this.
If anyone could share any information with me, it would be much appreciated!